Organic transistors are low in cost, and have properties such as flexibility, foldability and the like. Therefore, organic transistors are suitable for applications such as electronic paper, flexible displays and the like, and paid to attention recently.
Organic transistors have a layer having charge (denoting hole and electron, the same shall apply hereinafter) transportability constituted of an organic material, and as the organic material, organic semiconductor materials are mainly used.
As the performance of an organic transistor, electric field-effect mobility and the ON/OFF ratio are important and depend significantly on an organic semiconductor material used in the organic transistor. Therefore, an organic semiconductor material is required to have high mobility. If an organic semiconductor material is oxidized, the ON/OFF ratio of an organic transistor tends to lower, thus, stability against oxidation is also required. When an organic semiconductor material has high ionization potential, it is liable to be stable against oxidation.
As the organic semiconductor material used in an organic transistor, poly(3-hexylthiophene) as a polymer compound is suggested, and an organic transistor using the polymer compound shows an electric field-effect mobility of about 10−5 to 10−2 cm2/Vs and an ON/OFF ratio of 104 or less (non-patent document 1). The ionization potential of poly(3-hexylthiophene) is about 5.0 eV which is not necessarily recognized as high, thus, it is liable to be oxidized.
As the organic semiconductor material used in an organic transistor, the following polymer compound having a naphthalene structure, a thiophene structure and a benzothiadiazole structure is suggested, and the electric field-effect mobility of an organic transistor using the polymer compound is 0.003 cm2/Vs (patent document 1).
